Interhemispheric connections between olfactory bulbs improve odor detection
Fig 3
Interhemispheric connections modulate odor-evoked responses in the contralateral OB.
(A) Illustration of the experimental setup depicting an adult zebrafish brain explant expressing GCaMP6s in mitral cells. A tube delivers food odor (od) selectively to the ipsilateral nostril. Contralateral stimulations (cs) of varying intensities (low, medium, and strong, see Materials and methods) are delivered using a glass microstimulation electrode inserted in the contralateral olfactory nerve. (B) The contralateral olfactory tract, which enables interhemispheric olfactory connections, is sectioned in control conditions. (C–E and O) Mean odor response time course of all mitral cells recorded in the ipsilateral OB following odor presentation (od, gray bar) or odor combined with simultaneous contralateral microelectrode stimulation (od + cs; cs indicated by a red bar) for low, medium, and strong stimulation intensities and the control condition, respectively. For each condition, mitral cells from multiple animals are pooled and sorted by the amplitude of contralateral modulation ([od + cs] − od). (F–H and P) Average mitral cells’ responses to odor (red) are plotted against their response to odor combined with cs for low, medium, and strong cs (in red) and the control condition (in black), respectively. Mitral cells above the unity line are positively modulated by contralateral inputs. (I–K and Q) The contralateral modulation ([od + cs] − od) is displayed for all mitral cells for low, medium, and strong cs and the control condition, respectively. (L–N and R) The cumulative frequency distribution of the contralateral modulation is displayed for all mitral cells for low, medium, and strong cs (in red) and the control condition (in black), respectively. The numbers of mitral cells are as follows: low cs, 335 cells in three fish; medium cs, 335 cells in three fish; strong cs, 857 cells in six fish; control cs, 477 cells in two fish (*p < 0.05; ***p < 0.001; two-sample, two-tailed Kolmogorov–Smirnov test). Numerical data used to generate this figure can be found in S1 Data and S2 Data. cs, contralateral microstimulation; GCaMP6, genetically encoded calcium sensor, circular permutated green florescent protein-Calmodulin-M13 peptide 6; OB, olfactory bulb; od, food odor extract.